The design and construction of electric motors is a very highly developed and mature art. An extensive variety of motor configurations, including both basic modifications of the design concept and less drastic but no less significant modifications of the design parameters have been used. Within this context, modifications which produce even minor improvements in performance, size or cost are difficult to achieve.
A further aspect of the context of this invention is that the motor designs previously utilized have presented difficulties in terms of the practical utility of the motor. Particularly in portable motor-driven devices, but also in other applications, the motor is mounted in a structure which must serve as an adequate housing for the motor and simultaneously as the exterior surface which is used, handled and carried by the operator. Appliances presently available are frequently compromises which sacrifice either motor performance or practical utility or both.
Presently known motor designs have been developed from the original designs made for use with hand-inserted coils. Although modern designs have been adapted to automatic winding equipment and although extensive efforts have been made to improve the efficiency of motors, including efficiencies of power, space, steel or wire usage, and mounting, these efforts have not produced the improvements desired. In general, the motors resulting have been approximately square or rectangular, resulting in poor space, steel usage and mounting efficiencies, or round, resulting in poor power, wire usage and mounting efficiencies. The present invention is directed to a conceptually new design for these motors which permits substantial improvement in all of these categories, and to an improved class of power tools incorporating this design.
It is, accordingly, an object of this invention to provide a new and improved universal or D.C. motor for use in electric power tools and appliances.
It is also an object of this invention to provide new and improved tools and appliances permitted by an improved electric motor construction.
Another object of this invention is the provision of a new and improved field for two pole wound universal or D.C. motors.
A further object of this invention is the provision of a new and improved field lamination for use in universal or D.C. electric motors, particularly for power tools.
It is also an object of this invention to provide a new and improved two pole universal or D.C. motor which is readily accommodated within a smaller housing without adversely affecting motor performance.
Another object of this invention is the provision of a new and improved universal or D.C. motor which is easily mounted in a variety of housing configurations.
It is also an object to provide a two pole universal or D.C. motor field which enable maximum performance to be obtained from a given motor size.
A further object of the provision of a new and improved field lamination for a two pole electric motor which may be mounted in housings of preferred external configuration without loss of performance.
It is a specific object of this invention to provide an improved field for use in a light-weight, hand-held appliance having an electric motor in an enclosure driving an output shaft, the motor being of the type having a two-pole wound field and a commutated armature. The improved field includes a substantially hexagonal yoke structure surrounding the armature and a pair of poles disposed within the yoke structure at diametrically opposed locations. Each of the poles is located in the center of one side of the hexagonal yoke structure and a pair of pole tips extends from each of the poles so that a winding slot is defined between each of the pole tips and the portion of the yoke structure adjacent thereto.
Another specific object of this invention is an improvement in two-pole wound fields of the type used in light-weight, hand-held appliances including an enclosure, an electric motor within the enclosure driving an output shaft and a commutated armature associated with the field, wherein the improved field includes a substantially hexagonal yoke structure surrounding the armature and a pair of poles disposed within the yoke structure at diametrically opposed locations. Each of the poles is located in the center of one side of the hexagonal yoke structure. A pair of pole tips extends from each of the poles and a winding slot is defined between each of the pole tips and the portion of the yoke structure which is adjacent thereto. Each of the poles includes a throat portion between the yoke structure and the pole tips, and the throat portion has a minimum thickness between the bottoms of the winding slots of approximately twice the width in cross section of the yoke structure.
It is also a specific object of this invention to provide an improved two-pole wound field motor of the type using a commutated armature and adapted for use in a light-weight, hand-held appliance wherein the motor is placed within an enclosure and drives an output shaft, the improved motor including a field having a substantially hexagonal yoke structure surrounding the armature and a pair of poles disposed within the yoke structure at diametrically opposed locations. Each of the poles is located in the center of one side of the hexagonal yoke structure and a pair of pole tips extends from each of the poles. A winding slot is defined between each of the pole tips and the portion of the yoke structure which is adjacent thereto. Each of the portions of the yoke structure which is adjacent a respctive winding slot includes one of the corners defined between the sides of the hexagonal yoke structure so that each of the winding slots includes the additional area provided by the corner. The corner is located within the lower half of the arcuate length of the winding slot as measured from the bottom of the slot outwardly toward the end of the pole tip.